Modern disc drives are commonly used in a multitude of computer environments, ranging from super computers to notebook computers, to store large amounts of data in a form that is readily available to a user. Typically, a disc drive has one or more magnetic discs that are rotated by a spindle motor at a constant high speed. Each disc has a data storage surface divided into a series of generally concentric data tracks that are radially spaced across a band having an inner diameter and an outer diameter. The data is stored within the data tracks on the disc surfaces in the form of magnetic flux transitions. The flux transitions are induced by an array of read/write heads. Typically, each data track is divided into a number of data sectors where data is stored in fixed size data blocks.
The read/write head includes an interactive element such as a magnetic transducer. The interactive element senses the magnetic transitions on a selected data track to read the data stored on the track. Alternatively, the interactive element transmits an electrical signal that induces magnetic transitions on the selected data track to write data to the track.
Each of the read/write heads is mounted to a rotary actuator arm and is selectively positioned by the actuator arm over a pre-selected data track of the disc to either read data from or write data to the data track. The read/write head includes a slider assembly having an air bearing surface that, in response to air currents caused by rotation of the disc, causes the head to fly adjacent to the disc surface with a desired gap separating the read/write head and the corresponding disc.
Typically, multiple center-open discs and spacer rings are alternately stacked on a spindle motor hub. The hub, defining the core of the stack, serves to align the discs and spacer rings around a common axis. Collectively the discs, spacer rings and spindle motor hub define a disc pack assembly. The surfaces of the stacked discs are accessed by the read/write heads which are mounted on a complementary stack of actuator arms which form a part of an actuator assembly. The actuator assembly generally includes head wires which conduct electrical signals from the read/write heads to a flex circuit which, in turn, conducts the electrical signals to a flex circuit connector mounted to a disc drive base deck.
When the disc drive is not in use, the read/write heads are parked in a position separate from the data storage surfaces of the discs. Typically, a landing zone is provided on each of the disc surfaces where the read/write heads are positioned before the rotational velocity of the spinning discs decreases below a threshold velocity which sustains the air bearing. The landing zones are generally located near the inner diameter of the discs.
Two continuing trends in the disc drive industry are in the reduction in physical size and in increased data storage capacity. As a result, the disc pack has been increasingly made smaller, requiring the use of thinner discs with tighter disc-to-disc spacing. The areal density of stored data has steadily increased, heightening the positioning precision requirements of the read/write head in relation to the rotating disc.
Although providing increasing amounts of storage capacity, these changes give rise to a problem of increased sensitivity to operational resonance. Additionally, these changes significantly increase the likelihood that external mechanical shock and vibration will result in physical contact between the actuator assembly and the disc surfaces and thereby damage stored data. Absent physical contact, certain frequencies can also cause the transducer to move off-track. That is, resonance can affect the ability of the servo system to maintain the transducer in a desired relation to a followed track and can lengthen the time required to settle the transducer onto a destination track at the conclusion of a seek.
In response to the continuing market demand for ever smaller disc drives and increased storage capacity there is a need in the industry for an improved disc drive apparatus that is capable of increased data storage capacity and which exhibits improved resilience to external forces and operational resonance.